Issued by NWS Grand Rapids, MI
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000 FXUS63 KGRR 251916 AFDGRR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 314 PM EDT SAT OCT 25 2008 LATEST UPDATE...LONG TERM... .SYNOPSIS...(450 AM EDT SAT OCT 25 2008) LOW PRESSURE WILL MOVE NORTHEAST INTO CANADA...LEAVING BEHIND SCATTERED SHOWERS ACROSS THE REGION TODAY AND TONIGHT. A COLD FRONT WILL CROSS SOUTHWEST LOWER MICHIGAN EARLY SUNDAY MORNING. THIS FRONT WILL USHER IN COLDER AIR AND BRISK WINDS. SOME SNOW WILL BEGIN TO MIX IN WITH THE RAIN AND EVENTUALLY CHANGE TO ALL SNOW SUNDAY NIGHT. SOME LIGHT ACCUMULATIONS ARE POSSIBLE BY MONDAY MORNING. THE CHILLY AIR WILL HANG ON UNTIL MID WEEK. && .SHORT TERM...(450 AM EDT SAT OCT 25 2008) (TODAY THROUGH MONDAY) RATHER COMPLEX SCENARIO WILL UNFOLD THROUGH THE SHORT TERM AS MUCH COLDER AIR AND BLUSTERY WINDS WILL INVADE THE REGION BY LATE IN THE WEEKEND AND CONTINUE INTO MONDAY. AN UPPER LOW WAS OVER CENTRAL LAKE MICHIGAN THIS MORNING. THE LAST OF THE STEADY PCPN WAS MOVING NORTH OVER THE CWA ATTM. THIS WILL LEAVE JUST SCATTERED SHOWERS LINGERING FOR THE REMAINDER OF THE DAY THAT SHOULD NOT AMOUNT TO MUCH. A POWERFUL COLD FRONT WILL RACE ACROSS THE UPPER MIDWEST TONIGHT AND ACROSS LOWER MICHIGAN LATE TONIGHT. THIS FRONT IS BEING PUSHED ALONG BY A 155 KNOT JET STREAM THAT WILL CARVE OUT A DEEPENING UPPER TROUGH INTO THE FIRST PART OF THE WEEK. THE SHOWERS MAY BECOME A BIT MORE COMMONPLACE WITH THE FRONT. HOWEVER THE MAIN THRUST OF THIS SYSTEM WILL BE THE WIND WHICH WILL INCREASE AS THE FRONT PASSES WITH GUSTS OF 30 TO 35 MPH EXPECTED BY DAYBREAK. HAVE HOISTED A WIND ADVISORY FOR SUNDAY ACROSS THE LAKESHORE COUNTIES. THE WINDS WILL CONTINUE TO INCREASE AS THE COLD ADVECTION COMMENCES. BUFKIT PROFILES SHOW VERY DEEP MIXING WITH GUSTS IN THE ADVISORY AREA APPROACHING 50 MPH. THE WINDS WILL BE STRONG INLAND TOO...AND THE ADVISORY MAY NEED TO BE EXPANDED...BUT AS OF THIS POINT FEEL MORE CONFIDENT IN THE UNSTABLE LAKE ADDING ENOUGH TO PUSH TO LAKESHORE COUNTIES INTO ADVISORY WINDS. TEMPS WILL MAX OUT IN THE MORNING IN MOST PLACES...THEN FALL THROUGH THE AFTERNOON. SNOW SHOULD BEGIN TO MIX IN WITH THE RAIN ACROSS THE NORTHWEST HALF OF THE CWA BY LATE AFTERNOON. BLUSTERY CONDITIONS WILL CONTINUE INTO SUNDAY NIGHT. DEEP MIXING IS STILL INDICATED...SO THE WIND ADVISORY COULD NEED TO BE EXTENDED IN TIME BY LATER SHIFTS. DELTA T/S CLIMB TO AROUND 20 BY EVENING SO THE LAKE EFFECT SHOWERS SHOULD BEGIN OVERNIGHT. SOUNDINGS ARE SHOWING A BIT OF A DRIER LAYER NEAR THE BOUNDARY LAYER WHICH COULD DELAY THE ONSET OF THE LAKE EFFECT. HOWEVER DEEPER MOISTURE ARRIVES BY LATE SUNDAY NIGHT...SO CONFIDENCE IS STILL HIGH IN LAKE EFFECT DEVELOPMENT. THE PCPN SHOULD CHANGE OVER THE ALL SNOW IN MOST PLACES LATE AS H8 TEMPS FALL TO -6C. WITH SUCH A WARM LAKE...AND THE BRISK WINDS...THE BEST LIKELIHOOD OF SOME LIGHT ACCUMULATIONS WILL BE FURTHER INLAND ALONG U.S. 131. THE FLOW SHOULD BE 295-310... FAVORING THE SW CORNER OF THE CWA. THE BEST CHANCE OF LAKE EFFECT APPEARS TO COME THROUGH MOST OF MONDAY WHEN DEEP MOISTURE IS PRESENT ALONG WITH COLD H8 AIR AND SOMEWHAT LIGHTER WINDS. THE PCPN TYPE SHOULD BE MOSTLY SNOW EARLY...BUT THEN BECOMING MIXED THROUGH THE DAY...KEEPING ANY ACCUMS ON THE LIGHT SIDE. && .LONG TERM...(314 PM EDT SAT OCT 25 2008) (TUESDAY THROUGH SATURDAY) FORECAST CONCERNS ARE FEW DURING THE EXTENDED PERIOD AND MAINLY DEAL WITH PCPN TRENDS TUESDAY. THE DEEP UPPER LOW MOVING THROUGH THE GREAT LAKES WILL BE MOVING INTO NEW ENGLAND BY TUESDAY MORNING. A HIGH AMPLITUDE UPPER RIDGE WILL TAKE ITS PLACE. TEMPS WILL SLOWLY RISE TO THE UPPER 50S BY THE END OF THE WEEK AS THE RIDGE SLIDES EAST. BOTH THE GFS AND ECMWF SHOW A SHORT WAVE UNDERCUTTING THE TROUGH FRIDAY AND MOVING THROUGH THE OHIO VALLEY. THE GFS IS STRONGER AND A LITTLE FARTHER NORTH WITH THIS WAVE THAN THE ECMWF IS. WE/RE NOT GOING TO ADD PCPN TO THE GRIDS AT THIS POINT FOR THIS FEATURE...BUT WILL INCREASE CLOUDS IN THE SW TO ACCOUNT FOR IT. && .MARINE...(450 AM EDT SAT OCT 25 2008) HAVE UPGRADED THE GALE WATCH TO A GALE WARNING AND MOVED THE TIMING UP TO LATE TONIGHT. THE FRONT APPEARS TO MOVE THROUGH THE LAKESHORE WATERS BY DAYBREAK SUNDAY AND THE GALES WILL BE ON THE HEELS OF THE FRONT. HAVE 45 KNOT GALES MENTIONED INTO SUNDAY AND WE ARE PROBABLY LOOKING AT BORDERLINE STORM FORCE WINDS. WILL LET FUTURE FORECAST CYCLES MONITOR THE NEED TO A POSSIBLE UPGRADE TO A STORM WARNING. && .AVIATION...(157 PM EDT SAT OCT 25 2008) SHOWERS WILL EXIT THE CWA THIS AFTERNOON LEAVING GENERALLY DRY WX THROUGH THE EVENING AND EARLY OVERNIGHT HOURS. CIGS WILL SLOWLY LIFT TO VFR CONDITIONS BY LATE IN THE DAY. MVFR CIGS WILL RETURN WITH A STRONG COLD FRONT AROUND 12Z SUNDAY. LAKE EFFECT SHRA EXPECTED FOR THE LAST 6 HRS OF THE TAF PERIOD. && .HYDROLOGY...(450 AM EDT SAT OCT 25 2008) RAINFALL FROM YESTERDAY WAS GENERALLY AROUND AN INCH ACROSS THE SOUTHWEST HALF OF THE CWA...AND SOMEWHAT LESS OVER THE NE. ALTHOUGH RIVERS ARE ABOVE AVERAGE...THIS CAN STILL BE HANDLED WITH JUST SOME RISES. RAINFALL TODAY THROUGH SUNDAY SHOULD A QUARTER INCH OR LESS. STEADIER LAKE EFFECT PCPN CAN BE EXPECTED ALONG THE LAKESHORE SUNDAY NIGHT INTO MONDAY. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...WIND ADVISORY FOR THE LAKESHORE COUNTIES ON SUNDAY. LM...GALE WARNING IN EFFECT FROM ST JOE TO MANISTEE LATE TONIGHT THROUGH MONDAY AFTERNOON. && $$ SYNOPSIS: JK SHORT TERM: JK LONG TERM: 93 MARINE: JK AVIATION: 93 HYDROLOGY: JK
